/**
 * Copyright 2013-2014 Guoqiang Chen, Shanghai, China. All rights reserved.
 *
 * Email: subchen@gmail.com
 * URL: http://subchen.github.io/
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package jetbrick.lang.concurrent;

import java.util.concurrent.atomic.AtomicReference;

public abstract class AtomicSafeInitializer<T> implements ConcurrentInitializer<T> {
    private final AtomicReference<AtomicSafeInitializer<T>> factory = new AtomicReference<AtomicSafeInitializer<T>>();
    private final AtomicReference<T> reference = new AtomicReference<T>();

    @Override
    public final T get() {
        T result;
        while ((result = reference.get()) == null) {
            if (factory.compareAndSet(null, this)) {
                reference.set(initialize());
            }
        }
        return result;
    }

    protected abstract T initialize();
}
